COMSTOCK — STUDIES IN ASTRONOMY 63 



The coefficients in equations A and B have been so de- 

 termined as to reproduce with all possible fidelity the re- 

 fractions of the Pulkowa Tables, but they may be made to 

 represent the actual refractions -with greater pre- 

 cision by the application to the constant coefficients of the 

 formulae of certain'corrections depending upon the latitude 

 of the place at which the refraction is required, the amount 

 of moisture in the air and the wave length of the light 

 whose refraction is to be computed. These corrections are 

 developed in Vol. IX, Publications of the Washburn Ob- 

 servatory. The most important of them, and the only one 

 which need be considered here, is that depending upon the 

 latitude. Its effect will be sufficiently taken into account 

 by adding to the bracketed coefficient in the equations A 

 and B, the quantity 



C = 225 sin {q> - GO^) sin (9 + 60^) 



where cp denotes the latitude and C is given in units of the 

 fifth decimal place. 



